1. Field of the Invention
The present invention relates to an illumination device. In particular, the illumination device of the present invention is easily moldable as a part and is strong to environment variations with a high precision when assembled as a unit in which a point light source and a cheap, light, resin material based reflective member are used.
2. Description of the Related Art
In recent years, developments of light emitting diodes (LED hereinbelow) are performed actively and brightness of LED elements has increased drastically. LED generally has advantages of long life span, high efficiency, high shock absorbing properties and single color emission or the like and applications to a variety of fields of illumination are expected. As one of the purposes of usage, an LED can be used for an image reading apparatus of a digital copier or an image scanner or the like. However, although the current LED has the above described excellent properties, in order to be used for an illumination device of an image reading apparatus, an absolute brightness of a single LED is insufficient. As a result, LED is mostly used around a low speed reading device or a device with emphasis on light weight and compactness. On the other hand, mainly cold cathode fluorescent lamp is used for a high speed reading device and a device of large size. By the way, JP2006-067551A and JP2006-042016A are proposed as conventional technologies in which various innovations are performed so that LEDs are used for an illumination device and an image reading apparatus.
[Descriptions with Regard to a Prior Application]
An illumination device (manuscript illumination device) has been applied by applicants of the present invention in which LEDs are used as light sources (Japanese Patent Application No. 2008-041540). This application uses light sources that drastically save energies in comparison to light sources of tube lamps in order that a small sized illumination unit can be realized so that further energy saving is realized. This application provides a manuscript illumination device or the like of the above objects.
In order to realize the above objects, the manuscript illumination device is constituted as illustrated in FIG. 1. FIG. 1 is an approximate side cross sectional diagram of the manuscript illumination device. As illustrated in FIG. 1, in an illumination system, that is, the manuscript illumination device, LEDs are used as light sources. A reflective surface is disposed between a distance from LEDs arrayed in a longitudinal direction of an irradiated surface to the irradiated surface in order that a light path length can be extended and illumination intensity irregularities in the longitudinal direction of the irradiated surface can be suppressed. In addition, light use efficiency can be improved by optimizing a shape of the reflective surface. However, in this prior application, the reflective surface is thin walled with a broad area of plain surface part. A constitution is adopted in which the reflective surface is connected only at end parts so that the reflective surface must be molded as a part in which a certain degree of flatness is ensured. In addition, by flexures due to self weight or deformation of the reflective surface due to thermal expansion or the like, properties of the above described illumination system can deteriorate. This is a respect that must be necessarily considered when a structure body is set to be made of resin from aims for light weight and small size.